Diagnostic value of two-dimensional echocardiographic measurements of the pulmonary artery diameter and the pulmonary artery distensibility index to detect pulmonary hypertension in horses

Introduction/objectives

Echocardiographic diagnosis of pulmonary hypertension (PH) in horses is usually based on Doppler interrogation of tricuspid (TR) or pulmonic regurgitation (PR). This study aimed at investigating two-dimensional echocardiographic (2DE) variables, including pulmonary artery diameter (PAD) and pulmonary artery distensibility index (PADI), to diagnose PH.

Animals, materials and methods

41 healthy horses; 82 horses with TR or PR and normal intracardiac pressure gradients; and 35 horses with TR or PR velocities indicating PH. The 2DE variables were compared between groups, cut-offs for the diagnosis of PH were determined, and conditional inference trees served to identify the variable best predicting PH in the absence of TR or PR.

Results

Horses with PH had larger end-diastolic cross-sectional (short-axis) PAD (PAD_ed-sx) (5.8 ± 1.0 cm; mean ± SD) and smaller PADI_[/PADps] (15.4 ± 7.7%) than healthy horses (5.0 ± 0.6 cm, P<0.0001; 20.5 ± 4.4%, P<0.001) and horses with TR or PR but no PH (5.3 ± 0.6 cm, P=0.003; 18.8 ± 4.2%, P=0.005). PAD_ed-sx predicted PH with sensitivity (Se) = 36% and specificity (Sp) = 94% (cut-off 6.0 cm, AUC = 0.668, P=0.002), while PADI_[/PADps] predicted PH with Se = 43% and Sp = 92% (cut-off 13.7%, AUC = 0.662, P=0.004). In the absence of TR, PAD_ed-sx and the end-diastolic long-axis aortic diameter-to-PAD_ed-sx ratio (AoD_ed-lx/PAD_ed-sx) were most suitable to diagnose PH.

Conclusion

PAD_ed-sx and PADI were moderately specific but not very sensitive to diagnosing PH. Nonetheless, they may be used as complementary indices suggesting PH in the absence of TR or PR.